


Deepthroating

by PineTrain



Category: Gravity Falls
Genre: F/M, pinecest - Freeform
Language: English
Status: Completed
Published: 2017-04-08
Updated: 2017-04-08
Packaged: 2018-10-16 11:55:33
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 898
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10570806
Author URL: https://archiveofourown.org/users/PineTrain/pseuds/PineTrain





	

Dipper was only doing this because Mabel wanted to. He was totally game for it, but he’d never think to actually ask this of her even though he had always secretly hoped the answer to that question was ‘yes’. 

Turns out it was, apparently. His sister lay on her back naked atop his desk in front of him, adjusting herself to be as comfortable as possible before relaxing her head off its edge. Satisfied with her position, Mabel grinned at him seductively. She beckoned with a finger as she opened her mouth wide with her tongue out. 

Dipper approached her, shaking a bit from both nerves and excitement. Mabel had given him blowjobs before but deepthroating was a whole nother level. They figured the angle this gave would make things easier and Mabel assured him she’d done some practicing on the side. He still couldn’t help but hesitate just a millimeter from her mouth, last second jitters getting to him. Mabel nudging out to give a lap at his dick made him wince and fall forward. 

Catching himself with his hands on the desk he unintentionally crammed his member into her mouth. Mabel jolted in surprise and he tried to pull out, worried he’d hurt her. But she grabbed his ass with her hands to stop him. She ran her tongue around his head in a sign that everything was alright. 

Dipper still couldn’t get over his fear of hurting her. Mabel must have recognized this because her tongue continued to play with him, consistently pulling back towards her throat in encouragement. Dipper obliged, slowly slipping more into her mouth until he hit some resistance. 

This was the edge and Mabel spanking his ass pushed him over it. Tight muscles wrapped around him, tighter even than when they had sex. Mabel flinched and he almost pulled out, but she held him in place with her hands. So he pushed forward, shivering as that tight sensation spread down his shaft. 

Eventually, he felt his balls on Mabel’s nose. She hummed in satisfaction and Dipper scratched some of the varnish off the desk at the tingling coursing through him. He took a second to catch his breath from his panting. 

Oh, breath. Mabel could probably use some. He pulled back and heard her take in a large one through her nose. As awesome as that had been, Dipper still worried about her. Mabel spanked him again though and he thrust back in from surprise. She gagged and the feeling of her throat spasming made him tremble. 

He must’ve hurt her, but then she was holding him fast as she waited it out. Did that mean she didn’t mind it? Dipper was feeling less and less in control of his desire as he looked down to see Mabel’s throat bulging. She swallowed and he watched her muscles travel down his length just as he could feel it. He pulled out again. Mabel took another breath and he slid his hand into her hair, placing it between the back of her head and the desk. 

“Mabel…” he said, trying to convey what his lust-fogged mind was pushing him to do. The lick she gave him inside her mouth seemed like confirmation that she understood. Dipper pulled back just a bit as Mabel took a deep breath. He thrust in, going all the way to the hilt in half a second. 

He looked down at her throat to watch the bulge recede as he pulled out before thrusting in again. Mabel’s lips left his cock as she opened her mouth wider to prevent her teeth scraping him as he picked up a rhythm. He fucked her face until her legs began writhing and he realized he should stop. She coughed a bit around his dick but lightly held him in place with her teeth when he tried to remove himself. 

She leaned to meet his eye around his shaft, demanding he finish this. He was close anyways so Dipper didn’t have to concern himself with going too long. A few more thrusts and he found himself collapsing onto his elbow, fully engulfed in his sisters throat. Just one more would be enough but he was shivering too hard on the precipice to move. 

It was agonizing but he was stuck in some kind of perfect balance of desire and weakness that he just couldn’t do it and couldn’t bring himself to give up. Fortunately, Mabel always had his back. She swallowed again, her clenching muscle giving him that needed release. 

He grunted as his hand shoved Mabel deep into his crotch while he sent his seed straight into her stomach. Finishing, Dipper stepped backwards, finally removing himself from Mabel’s mouth, a thick trail of mixed saliva and cum connecting his cock and her mouth. It broke when she coughed, partially smearing up her eye before it fell to the floor. Dipper fell on his ass in exhaustion while Mabel rolled off his desk to settle on her knees. 

She wiped the streak off her face, licking it off her finger and smirking at him. Dipper smiled back at her, but this wasn’t the end of it. 

He had a surprise for her too. Something he’d needed to practice just like she had. He looked over towards his bed, their new low angle showing the box underneath. He hoped she’d like the strap-on inside. 


End file.
